1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a laser printer, or a facsimile machine based on an electrophotographic scheme.
2. Description of the Related Art
In a conventional electrophotographic image forming apparatus, the surface of a photosensitive drum is charged and exposed to light by an exposure unit to form an electrostatic latent image. Then, the electrostatic latent image is developed into a toner image by a developing unit using toner. The toner image is then primarily transferred to an intermediate transfer belt. To form a color image, the above-described steps are repeated to form a color toner image on the intermediate transfer belt. The formed color toner image is secondarily transferred to a recoding material. Thereafter, the color toner image on the recording material is fixed by a fixing unit.
In connection with the secondary transfer of a color toner image to a recording material, a configuration has been known in which a transfer bias is applied to a transfer roller that contacts and conveys the recording material.
Toner may adhere to the transfer roller. Japanese Patent Application Laid-Open No. 2000-029281 discloses cleaning of the adhering toner by means of application of a cleaning transfer bias to the toner.
The transfer roller serves to contact and convey a recording material. Thus, in many cases, paper dust adheres to the transfer roller. The paper dust adhering to the transfer roller is often charged owing to the effect of a transfer bias or sliding friction against the roller.
In recent years, there have been demands to increase the operating speeds and lives of image forming apparatuses. Furthermore, with distribution of a variety of recording materials, image forming apparatuses have been desired to demonstrate an improved transfer capability and enhanced durability with respect to any recording materials. In the conventional art, when, in particular, a large amount of recycled paper or vile paper, a large number of recording materials containing a large amount of loading material such as talc, or a large amount of paper involving a large amount of paper dust passes through the image forming apparatus, a large amount of paper dust may adhere to the transfer roller. As a result, the transfer capability may be degraded.